contr.sdif {MASS}R Documentation

Successive Differences contrast coding

Description

A coding for unordered factors based on successive differences.

Usage

contr.sdif(n, contrasts = TRUE)

Arguments

n The number of levels required.
contrasts Should there be n - 1 columns orthogonal to the mean (the default) or n columns spanning the space.

Details

The contrast coefficients are chosen so that the coded coefficients in a one-way layout are the differences between the means of the second and first levels, the third and second levels, and so on.

Value

If contrasts is TRUE, a matrix with n rows and n - 1 columns, and the n by n identity matrix if contrasts is FALSE.

References

Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S. Fourth Edition, Springer.

See Also

contr.treatment, contr.sum, contr.helmert

Examples

contr.sdif(6)

[Package MASS version 7.2-33 Index]